Not exactly connected to version of moodle but permissions, settings and use of tex filter.
That debugging message most likely means that your moodle 2.4 site does not have local distribution of latex installed and therefore these executable files are not "readable" - they do not exist at all. So if your moodle was using tex filter on the same site in version 2.3 it was probably using executable mimetex file in folder filter/tex and you should make this mimetex executable file executable (change the permissions).
If debugging is set to ALL you might get some other messages about failure of using tex filter.
There are other Latex renderer options available too like adding MathJax script tags to Site administration > Appearance > Additional HTML ...